On Xiao Yan page there is a bit conflict on his page so im gonna try and figure his age out now on this blog. Please do comment below on your own opinion. First lets use the light novel as the source rather than the manhua. At the start of the manhua Xiao Yan was at the age of 15, with 16 being the age where he must attend the coming of age ceremony. While he was 15, Xiao Xun was 14, Nalan Yanran came to have the marriage of Xiao Yan and Nalan Yanran removed. They then made a promise of 3 years, then when he was 16 he applied for the Jia Nan Academy and asked for a year break to train. With these sources we can guess that Xiao Yan is 18, because he actually reached Jia Nan Academy a year late and made Xiao Xun wait for him for 2 years in Jia Nan Academy. There is abit of conflict on his age due to the manhua source since when the time flow differently since Xiao Yan only had 6 month for the Ceremony and when he became a 2nd rank Receptarier, it was announced that he was 19 however if you looked closely Xiao Yan never mentioned his age to the receptarier so this age might have been a guessed. He was also announced the youngest receptarier to reach 2nd rank receptarier which is also very wrong since Princess Yu Er reached 3rd rank at the age of 14. So i think until the manhua announce his official age I'm gonna use the light novel as his age.